The empty containers or boxes with fixed side walls need considerable storage space. Therefore, the existing container comprises collapsible side walls to reduce the corresponding volume in unloaded status. Most of these collapsible containers comprise a base in form of rectangular plate structure, wherein the collapsible side walls are coupled to the edges of the base by hinges. When the side walls are in unfolded position, the side walls are coupled to each other via interlocking buckle engagement, wherein engaging latches on one pair of opposite side walls are engaged to the engaging hooks on the other pair of opposite side walls.
For many containers, the side walls are configured to be higher than half of the width of the base, thus the opposite side walls will be overlapped when they are folded towards each other. Therefore, the side wall which is folded later will extend beyond the edge of the side wall which is folded first and will be not parallel to the base but angled. In other word, the side wall folded later is in an inclined position. When a plurality of containers are stacked one above another, corresponding bending movement of the upper side wall positioned angularly occurs, which will cause a damage or deform over time. For such containers, another defect is that several collapsed containers can not be stacked in a stable way.
In order to overcome these defects, the side walls are connected to the shaft with different heights on the sides of the base, so that the side walls are connected to the base at different heights, wherein the side walls connected at lower positions are folded firstly, then the side walls connected at higher positions are folded subsequently, and when two side walls are in folded positions, they are arranged parallel to the base.
However, the height of the opposite side walls are different, which increases the cost of manufacturing and maintaining. Further, the workers must pay more attention during the operation which will affect the efficiency to some extend, since the folding work should be executed sequentially. It needs a more advanced alternative solution to solve this problem.